Hydrophone cable



June 3, 1958 w. T. HARRIS HYDROPHONE CABLE April 19. 1955 Filed nrnnornonn CABLE l Wilbur' 'll'. Harris, Southbury, Conn., assigner to The Harris Transducer Corporation, Woodbury, Conn., a corporation of Connecticut Application April19,l1955,vSerial No. 502,434-

1 Claim. (Cl. 340-17) My invention relates to electro-ac.' usticv transducers and, in particular, to arrayed constructions thereof. This application is a continuation-in-part of my copendingapa plication Serial No. 283,689, led April 22, 1952 which has issued as Patent No. 2,408,742, dated May 17, 1955.

It is an object of the invention to provide an-improved trnsducer array of the character indicated.

@rates Patent It is another object to provide an improved underwater transducer array which may lend itself to electric steering.

It is a further object to provide an underwater trans-y ducer array which is substantially neutrally buoyant.

A still further object is to provide improved cabling means for underwater acoustic arrays.

It is a general object to meetV theabove objects with a rugged, integral cable-transducer constructionvwhich will lend itself to a shipboard handling, as whenl neces'- sary ,to pay the cable in and out.`

Other objects and various further features of noveltyy Fig. 3 is a simplified diagram illustrating electricalconnections for the cable of Fig. 2;

Fig. 4 is a diagram similar to Fig. 3, but illustrating:

an alternative connection;

Fig. 5 is an enlarged fragmentary view in partial longitudinal section, illustrating an alternative `construction for a part of Fig. 2; and

Fig. 6 is another fragmentary view in partial longitudi-V nal section, illustrating an alternative for anotherpart of Fig. 2.

Briefly stated, my invention contemplates an improved electro-acoustic array comprising a plurality of electroacoustic devices integrally formed with the connecting cable. The electro-acoustic devices may be simply cylindrical or annular members incorporating means electrically responsive to stress resulting from radial deflection of said members. rl`he members may surround the cable at spaced locations depending upon the desired acoustic properties of the array. The cable may be of the multi-conductor variety and have a -ilexible tension core, as of stranded steel. At the point of attachment of each transducer to the cable, pressure-release `means may be provided of a sufficient volume to give the cable neutrally buoyant properties and, if desired, vthese properties may be enhanced by provision of annular floats integral with the cable at appropriate spacings. Ruggedness is achieved by employment of novel reinforcements and by using sound-transmitting potting materials of suitl able toughness.

Referringy to the ldrawings,.l indicate generally in'Fig.

1 that myarray may comprisev a plurality of transducer elements.V ltlspaced longitudinally alonga singlev cable.- 11,1l and suitably supported for the intended purpose.` In` the .case shownin Fig.'.l, the `cable is to be employed for underwater oil-prospecting, and I show the cable llbeing payed out from a drum 12;' supportedV at the, sternof a towingvvesselylS. Thevarious hydrophones lll'on` thefcable-11 may themselves be sutiicientlyneutrally buoyantfbun'if desired, additional'buoyancy maybe provided `by novelfloats 14`spaced from the hydrophones 11.,

The oat and hydrophonelconstructions` are shown in greater detail in Fig..- 2.

As-Will befseenfrom Fig..2, the supporting'cable` 11l may beof the` multi-conductor variety (asf-indicated schef matically by spacedy longitudinally extending. lines 15.)

filling :the.annular'spacearound' atension core 16 which'` may be a stranded-stool cable. For ready identification,y

the conductors 1Sfmay be color-coded, and they may be immersed in a= layer or'volurne of insulating materialn17;: alternatively, the conductors `l-may be twisted as indi-- vidual pairs, separately insulated, and merely packedl around a plastic or rubber-coated stress core` 16, the iinmersion in` insulating materialk 17 beingkunnecessary in certain applications. the.r construction of the. cable 11 itself.

The'a'ssernbly of thecable Vllllmalyff-in all respects: be'

conventional except'that I; prefer,- at eac-h locationwhere ahydrophone liifis tofber-attached,-that a different pair of conductors 15 ("as; for example, the/ conductors 1-5 in Fig. 3) be brought into 4a-.slightly enlargedloopgforelectrical connection to each` particular .'hydropghone.

This loop may be gathered. andknotted externally -of the= fillingv 17 before applicationof the-cover 1S, so thatwhen the cover 18 is applied, a small bump in thefouter contour` will `show where incision must be made to gain access to the desired pair of conductors 15. The cover 18 may be of tough plastic,.such as vinyl, but I prefer to-use rubber or afrubber-like material, such as neoprene.

The hydrophoneunit 10 is, in each case, preferably non-directional and, therefore, small compared to a wavelength. The basic transducer elements themselves preferably continuously envelop the cable 11, and I have shown annular transducer means 19 surrounding ythe cable v11 andI slightly spaced therefrom. The annular member 19 may be aV hollow magnetostrictive cylinder, with electricall means such as a windingtoroidally enveloping the same, as disclosed in said application, Serial No. 283,689. However, in the` preferred form shown,V

'hydrophone unit `16 and, therefore, I show a second core element 19 ywith associated foils or electrodes Ztl-26 for Ithe Idevice 10. These foils may be connected with each other andl across the looped conductor pair 15' at each point yof connection tothe cable, as suggested at Fig. 3, the preferred connections to elements 19-1'9 being in parallel, as shown.

It will be understood that the transducer elements 1-9--19 for the hydrophone unit 10 may be connected.

to one pair -of conductors in the cable 11, and tha-t at another hydrophone-unit location the transducerwindings thereof may be connected to the same pair or to a different pair of conductors, depending upon the desired overall performance of t-he device. l When connected to different. pairs `of conductors at V different hydrophone locations, it will be understood that the array may lend Patented June 3,. 1958- A coatingV or jacket 1S completes itself to phased steering at the shipboard-receiving location, by employment of means which are known and are, therefore, not shown.

In the specic construction 4of Fig. 2, the transducer means 19-20 is protected against abuse by means of a reinforcement member 22 in the form of a cylindrical core, which may be of aluminum in order to reduce the density of the assembly. This core may be integrally formed with reinforcement anges at spaced locati-ons, or, as shown, rings 23-24 may be provided to ride on the cylinder 22. 'I'he rings 23-2'4 extend radially outwardly to an extent preferably at least equivalent to the outer dimensions of the transducer elements 19-19, and preferably slightly beyond, as shown. may then be potted with a sound-transmitting material 25 (such as a suitable plastic) in `the annular space dened between the reinforcement rings 23--24. I have shown a layer 26 of pressure-release material lining this annular space and riding on the outside of cylinder 22, so that the transducer means 19-19 may be primarily responsive to radial deformations due to external excitation.

After assembly, as described, on the cylinder 22,- the transducer-element Vassemblies may be guided over the cable I11 and electrically connected to the proper-conductor pair 15 at the desired location. Another layer 27 of plastic or other filling may then be applied to secure the cylinder 22 on the cable 11, and toprovide a tapered end for the assembly. Finally, la jacket 29 of rubber or rubber-like material, such as neoprene, may be applied over the entire device and faired into the cable jacket 18, as suggested in the drawing.

When the cable means 11 is of substantial length, it becomes important that lthe electrical parameters of all conductor pairs 1'5-15, etc., be substantially the same. This may be readily achieved by making sure that all lines 15-15 are of substantially the same length, as suggested in Figs. 3 and 4. 'In Fig. 3, I show all lines to terminate at the far end of the cable in lan open-circuit condition, as by casting the end of the cable in a block of insulating material, such as a block of plastic 31. Alternatively, all lines 15-15, etc., may be terminated with their characteristic impedances, as suggested in Fig. 4, where 4the impedances 32 (labeled Z0) close each line `and are cast in a single -block 33 for ruggedness.

AIn elongated cables of the character indicated, it is important to note that unless enough piezoelectricl cylinders are employed at each source location (e. g. for the two transducer elements 19-19 of the single unit 10 shown in Fig. 2) to make the source capacitan-ce high compared to the stray capacitance between lead -circuits 15 in the cable, then capacitative cross-talk between circuits is likely; in such event, a small impedance transformer 30 may be carried by each transducer unit 10 and serve to couple the elements 19-19 to the lead pair y15 associated therewith. In Fig. 2, I show that the impedance transformer 30 may conveniently be potted within a suitable protective recess 30 at one end of the reinforcement cylinder 22.

It is desirable that the overall density of the hydrophone unit 10, when assembled on the cable 11, shall be kept to a minimum, consistent with structural rigidity. To this end, the pressure-release means 26 may be of substantially greater volumetric proportions than those shown in the drawings, so as to render the hydrophone unit more nentrally buoyant. However, in the form shown, I have provided oat members, as at 14, -to improve the neutrally buoyant characteristic of the hydrophonic cable as a whole. The oat means 14 may comprise a cylindrical shell 35, tapered at one end 36, and with a hub 37 smoothly to ride the cable sheath 18' The shell 35 may dene an annular air pocket 38, providing the desired buoyancy, and resilient washer means 39may assure concentric mounting of the shell 35 on the cable 11. I have shown a cap member 40 iitting the open end The wound cores of the shell 35 and including a hub 41 riding the cable sheath 18. A jacket of rubber or rubber-like material 42 may encase the buoy structure 14, so as to protect the same against damage in handling. I prefer that external dimensions of the buoy and hydrophone units shall be approximately the same in order to improve the ease of handling on board ship, as well as for uniformity of appearance. v

In Fig. 5, I illustrate an alternative hydrophone-unit construction wherein an annular air pocket 45 provides the means 'for pressure-release internally of the transducer means i6- 47; like the transducer means 19-19' of Fig. 2, the transducer elements 46--47 may be two parallel-connected, foiled piezoelectric units. I have shown the air pocket 45 to .be defined by the cylindrical shell d3 upon which the members Afi64-7 and their potting 49 are supported. The cylinder 48 may be spaced from the cable 11 to the desired extent, as determined by a flange 50 on an end ring 51, and a further air pocket 52 may be provided at each end of the assembly by conical end pieces, such as the conical cap 53, tting over the flange ring 51 and including a hub 54 riding the sheath of cable 11. As before, a jacket 55 of rubber or rubberlike `material, such as neoprene, may encase the entire assembly so as to retain the same and so as to provide against damage in handling. l

In Fig. 6, I illustrate an alternative float construction having greater flexibility than that illustrated in Fig. 2. In the arrangement of Fig. 6, a corrugated metal bellows or sleeve 56 is held in radially spaced relation with the cable sheath 57, by means of rigid end caps; each end cap may comprise a conical member 58 on a sleeve 59 riding the cable sheath 57. A jacket 60 of rubber or rubberlike material may be applied over the entire oat unit and faired to the cable sheath to provide protection against damage in handling. l

It will be appreciated that I have described extremely rugged hydrophone-cable constructions, which may not only provide great resistance to damage in handling but which also possess enough inherent flexibility to permit handling with conventional cable rigs, such as drums and ship-board cable-paying apparatus. The construction lends itself to relatively simple fabrication, and the described transducer-element connections render the hydrophone cable particularly attractive for use in arrays, including steered arrays, extending for great distances.

While I have described the invention in detail for the preferred forms shown, it will be understood that modifications may be made within the scope of the invention as defined in the claim which follow.

I claim:

An electro-acoustic array, comprising a continuous elongated multi-conductor electric cable with a continu-V ous exible tension core and a plurality of transducer units connected thereto and supported thereon in longitudinally spaced relation, each transducer unit comprising a rigid cylinder secured to and coaxially surrounding a continuous part of said cable, an annular piezoelectric member supported by and coaxially surrounding said cylinder and in radially spaced relation therewith, rigid protective radial flanges carried by said cylinder at the longitudinal ends of said piezoelectric member, said anges extending radially outwardly of the periphery of said piezoelectric member, pressure-release means longitudinally coextensive with said piezoelectric member and radially intermediate said piezoelectric member and said cable, a potting of sound-transmitting material extending between said ilanges andintimately covering the periphery of said piezoelectric member and securing said piezoelectric member in radially spaced relation with said rigid cylinder, and impedance-matching means electrically connecting conductors of said cable to said piezoelectric member, the rigid frame constituted by said cylinder and by said flanges having adjacent one of said anges a protective recess accommodating said impedance-matchingV References `Cited in the le of this patent UNITED STATES PATENTS Harris May 12, 1953 Vogel Sept. 1, 1953 Harris May 17, 1955 

